The present invention relates generally to a file management device for managing WORM (Write-Once Read-Many) files, and more particularly to a file management device that deletes the WORM file in safety.
WORM (Write-Once Read-Many) has hitherto been actualized by way of a write-once type storage medium such as an optical disk. The WORM is a storage medium that is physically incapable of changing such as erasing and overwriting forever after being written once. Over the recent years, however, some disk apparatuses have come into existence, wherein a WORM function is provided on HDD (Hard Disk Drive) that is essentially erasable for the purpose of storing data.
A file management device for managing WORM files, when a retention period of the WORM file expires, automatically (or manually) deletes this WORM file. A system clock of the file management device handles the expiration of the retention period. A relatively high precision is therefore required of this system clock. Further, it is desirable that the management devices, servers, storages, etc. within the same network perform management based on the same fiduciary time as a timestamp (timestamp format) for the files to be managed so that the reference time is the same.
Another system is known (referring to, e.g., JP 3226158 B) in which, between service data management devices spreading across networks, one service data management device manages original data, while the other service data management device stores the data in order to utilize copy data. Then, as in JP 3226158 B, there is known a wide area distributed storage for storing the file in distribution via a wide area network by applying a method of storing copies of the same file in distant locations.
Such being the case, one known time unitary (time synchronization) management system exists, wherein time servers for managing nodes residing in the same network segment on the network on the basis of the same timestamp are provided on networks, and the time managed by the time servers is dealt with by the time unitary management using (implementing) NTP (Network Time Protocol) and so on.
Further, the time is managed by different time servers between different network segments. These different time servers periodically correct the time of the time servers by utilizing the standard time carried on radio waves, GPS (Global Positioning System), etc., thus keeping the time accurate. Therefore, big differences do not occur among even the different time servers.